Fluid treatment apparatus and method

ABSTRACT

A new apparatus for treating substrates with fluids, as well as a corresponding fluid treatment method, is disclosed. The new apparatus includes a new configuration of fluid jet injectors which substantially overcomes the problem of dragout, in which fluid impinged upon an area of a substrate is retained on that area, preventing fresh fluid from reaching the impinged area. This new configuration also avoids imposing torques on substrates, and substantially reduces the need for rollers and guides for transporting substrates.

TECHNICAL FIELD

This invention pertains generally to apparatuses and methods fortreating a substrate with a fluid, i.e., a liquid or a gas.

DESCRIPTION OF THE PRIOR ART

In the fabrication of a variety of devices such as, for example, printedcircuit boards, various fluid treatments are applied to correspondingsubstrates, including rinsing, drying, chemical etching and electrolyticprocessing. These fluid treatments have been carried out using dip tanksand various configurations of spray nozzles and fluid jet injectors.

Dip tanks, while useful, are disadvantageous because they require anundesirably large amount of time for mounting and unmounting substratesto and from racks or baskets which are submerged within the dip tanks.In addition, mass transfer within a dip tank is typically effected viadiffusion, which is often too slow a process to be economic. Forexample, when used for substrate rinsing, a dip tank quickly becomesheavily laden with the material to be removed from a substrate, whichreduces the diffusion rate within the dip tank, and thereby slowsrinsing. In fact, dip tanks often become so heavily laden with removedmaterial that further rinsing becomes impossible.

Spray nozzles are disadvantageous because, among other reasons, theyserve to atomize a fluid, resulting in the evaporation of the fluid. Asa consequence, undesirable chemical emissions are exacerbated and re-useof the fluid is precluded, both of which are uneconomic. In addition,because the sprays produced by spray nozzles typically fail to achievefluid bearing action on the substrates being processed, these substratesmust be transported to and from the sprays by rollers and guidespositioned between the spray nozzles and the substrates. However, thepresence of these rollers and guides is undesirable because, among otherreasons, they produce nonuniformities in the spray action which resultsin, for example, nonuniform rinsing and etching. Moreover, becausesprays quickly lose momentum, they often fail to achieve efficient fluidtreatment of specific substrate areas, which limits processing rate andthroughput. For example, sprays are often inefficient or ineffective inrinsing or drying specific substrate areas, such as the interiors ofholes in substrates, because whatever fluid reaches such areas tends tobe retained on or in these areas (a phenomenon called dragout), withrelatively little fresh fluid reaching these areas. Moreover, spraysoften re-deposit or re-position, rather than remove, debris on thesubstrate, which then requires the use of additional sprays.Consequently, the use of sprays often requires the use of an undesirablylarge amount of processing area, which is also uneconomic. Whileattempts have been made to orient sprays to achieve directionality andthereby overcome some of the above-mentioned disadvantages, theseattempts have typically been accompanied by a torque being imposed uponthe substrate by the directed spray. This results in instabilities inthe motion of the substrate, often causing jamming of the substrate inthe corresponding processing equipment, resulting in damage to thesubstrate or equipment, which is undesirable and counterproductive.

The use of fluid jets in the fluid treatment of substrates ispotentially advantageous because fluid jets exhibit directionality andtherefore, in principle, are capable of overcoming the disadvantages ofsprays. However, previous configurations of fluid jets have failed toovercome the problem of dragout, particularly in the case of substrateswith holes. Moreover, these previous fluid jet configurations have alsoimposed torques on substrates, resulting in undesirable andcounterproductive instabilities in the motions of substrates.

Thus, those engaged in the development of fluid treatment apparatusesand methods have long sought, thus far without success, fluid jetconfigurations which: (1) overcome the problem of dragout, particularlyin the case of substrates with holes; (2) avoid imposing torques onsubstrates; and (3) substantially reduce the need for rollers and guidesfor transporting substrates, thereby substantially reducing theinterference caused by such rollers and guides.

SUMMARY OF THE INVENTION

The invention involves a fluid treatment apparatus, and correspondingfluid treatment method, which substantially overcomes the problem ofdragout, which avoids imposing torques on substrates and substantiallyreduces the need for rollers and guides for transporting substrates. Inone embodiment of the inventive apparatus, at least one row of fluid jetinjectors penetrates a surface of the apparatus, over which a substrateto be processed is transported via rollers positioned at the entranceedge and exit edge of the apparatus surface. The substrate istransported in a direction which is substantially parallel to an axisassociated with the apparatus surface, extending from the entrance edgeto the exit edge, and the row of fluid jet injectors is alignedtransversely to this axis. During its transport, the substrate ispositioned close enough to the apparatus surface so that the fluid jetsemitted by the fluid jet injectors become immersed in a layer of spentfluid covering the surface, and therefore the emitted fluid jetsconstitute submerged fluid jets. Significantly, the row of fluid jetinjectors is positioned closer to the entrance edge of the apparatussurface than to the exit edge. As a result, the resistance to fluid flowtoward the exit edge, through the relatively long portion of the layerof spent fluid, is greater than the resistance to fluid flow toward theentrance edge, through the relatively short portion of the layer ofspent fluid. Consequently, after the fluid jets emitted by the fluid jetinjectors impinge upon the substrate, more than half the fluidassociated with the fluid jets flows countercurrently toward theentrance edge, where it is vented via, for example, drain holes in theapparatus surface. Thus, dragout is substantially eliminated becausefluid impinged upon the substrate is more readily removed afterimpingement, allowing fresh fluid to reach the substrate. In addition,the countercurrent flow prevents removed debris from being re-depositedor re-positioned on any portion of the substrate which has been impingedupon by the fluid jets. Moreover, the spent fluid layer and submergedfluid jets achieve a fluid bearing action on the substrate, reducing theneed for rollers and guides, other than the rollers at the entrance edgeand exit edge of the apparatus surface.

It must be noted that the substantial elimination of dragout via theinvention enables the inventive fluid treatment apparatus to fluid treatsubstrates more efficiently than was previously possible. Thus, forexample, the length of the inventive apparatus can now be much shorterthan was previously possible, which is highly advantageous.

To avoid a torque on a substrate which might be imposed by the use ofone row of fluid jets, the inventive apparatus preferably includes twosurfaces, with each containing one or more rows of fluid jet injectors,between which a substrate to be processed is transported. Here, thefluid jets which impinge upon the upper and lower surfaces of thesubstrate substantially balance each other, thereby substantiallyeliminating torques.

In another embodiment of the invention, intended to even more completelyeliminate dragout in substrates with holes, the inventive apparatusagain includes two surfaces, with each surface containing one or morerows of fluid jet injectors, between which a substrate is to betransported. Each row of fluid jet injectors on one surface is alignedwith a corresponding row of fluid jet injectors on the other surface.However, the fluid jet injectors of a row on one surface are offsetrelative to the fluid jet injectors of the corresponding row on theother surface so that if one were to project the former fluid jetinjectors onto the latter surface, the former fluid jet injectors wouldbe interdigitated with the latter fluid jet injectors. Thisinterdigitation of the fluid jet injectors ensures that the fluid jetswhich penetrate the holes in the substrate are unopposed bycounteracting fluid jets.

In yet another embodiment of the invention, the above-describedcountercurrent flow is achieved by providing at least two rows of fluidjet injectors on an apparatus surface over which a substrate is to betransported. Significantly, at least the second row of fluid jetinjectors is inclined toward the entrance edge of the surface. As aresult, the fluid jets emanating from the second row of fluid jetinjectors induce more than half the fluid associated with the fluid jetsemanating from the first row of fluid jet injectors to flow toward theentrance edge of the apparatus surface, after impingement upon thesubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described with reference to the accompanying drawings,wherein:

FIG. 1 is an isometric view of a first embodiment of the inventiveapparatus;

FIG. 2 is an end view of the embodiment shown in FIG. 1;

FIG. 3 is a top view of the embodiment shown in FIG. 1;

FIG. 4 is a top view of a second embodiment of the inventive apparatus;

FIG. 5 is a front view of the second embodiment of FIG. 4;

FIG. 6 is an isometric view of a third embodiment of the inventiveapparatus;

FIG. 7 is an end view of the embodiment shown in FIG. 6;

FIG. 8 is a top view of the embodiment shown in FIG. 6; and

FIG. 9 is a front view of the embodiment shown in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention involves a fluid treatment apparatus, and a correspondingfluid treatment method, which substantially overcomes the problem ofdragout, which avoids imposing torques on substrates and substantiallyreduces the need for rollers and guides for transporting substrates.These goals are achieved, in accordance with the invention, by employinga new configuration of fluid jet injectors in the inventive apparatus,producing a new configuration of fluid jets which impinge uponsubstrates undergoing fluid treatment, as more fully described below.

With reference to FIGS. 1 and 2, a first embodiment of the inventivefluid treatment apparatus 10 includes at least one plenum housing 20made, for example, of stainless steel, which contains a plenum chamber30 into which a fluid is fed under pressure via a feed tube 40. Theplenum housing 20 is topped by a connected injector plate 50 made, forexample, of aluminum. Significantly, at least one row 60 of at leasttwo, spaced-apart, drilled holes extends from the plenum chamber 30 tothe surface 52 of the injector plate 50, which holes serve as fluid jetinjectors.

As shown more clearly in FIG. 1, the inventive apparatus 10 alsoincludes rollers 80 and 90 which serve to transport a substrate 100,e.g., a printed circuit board substrate, at a distance, H, from thesurface 52, from an entrance edge 54 to an exit edge 56 of the surface52. This transport of the substrate 100 occurs along a direction whichis substantially parallel to an imaginary axis 110 associated with thesurface 52, which axis is oriented transversely to the entrance and exitedges 54 and 56, and extends from the entrance edge 54 to the exit edge56, and beyond.

While not shown in FIGS. 1 or 2, the inventive apparatus 10 preferablyalso includes side walls in flush contact with the flat end faces of theplenum housing 20, which side walls serve to confine the fluid emittedby the fluid jet injectors.

With reference now to FIG. 3, the at least one row 60 of fluid jetinjectors includes the fluid jet injectors 60-1, 60-2, 60-3, etc., withthe row 60 being inclined transversely to the imaginary axis 110.Preferably, each of the fluid jet injectors is of equal diameter, D,which ranges from about 5 mils 0.005 inches) to about 250 mils 0.25inches). Fluid jet injectors having diameters smaller than about 5 milsare undesirable because they are difficult to fabricate. On the otherhand, fluid jet injectors having diameters greater than about 250 milsare undesirable because they require an undesirably large amount of pumppressure to produce fluid jets.

With reference to FIG. 2, the drilled holes which constitute the fluidjet injectors are preferably all of equal length, L. In this regard, theratio L/D preferably ranges from about 0.5 to about 40. Ratios less thanabout 0.5 are undesirable because they result in poorly developed fluidjets. Ratios greater than about 40 are undesirable because thecorresponding fluid jet injectors are difficult to fabricate and requirean undesirably large amount of pump energy to achieve a useful flowrate.

With reference once again to FIG. 3, the fluid jet injectors arepreferably equidistantly spaced, with the center-to-center spacingbetween adjacent fluid jet injectors being denoted by S. The ratio S/Dis necessarily greater than one (a ratio S/D=1 implies the fluid jetinjectors are touching) but is preferably equal to or less than about20. Ratios greater than about 20 are undesirable because after thecorresponding fluid jets impinge upon the substrate 100, it has beenfound that the resulting fluid flows separate from the surface of thesubstrate 100 and form a region of recirculating fluid, which permitsundesirable re-deposition of debris or spent fluid.

With reference to FIG. 1, as noted above, the fluid jets injected by thefluid jet injectors are to be submerged fluid jets, i.e., the fluid jetsare to be injected into a layer of spent fluid covering the surface 52and substantially filling the space between the surface 52 and thesubstrate 100. Such submerged fluid jets are achieved, in accordancewith the invention, by bringing the substrate 100 into proximity withthe surface 52 so that the ratio H/D ranges from about 0.2 to about 15.Ratios smaller than about 0.2 are undesirable because the substrate 100is then so close to the surface 52 that the substrate is likely tobecome jammed against the surface 52. On the other hand, ratios greaterthan about 15 are undesirable because the substrate 100 is then so farfrom the fluid jet injectors that the corresponding fluid jets lose anundesirably large amount of momentum before impinging upon the substrate100.

It should be noted that the spent fluid layer and fluid jets achieve afluid bearing action on the substrate 100. As a consequence, the needfor rollers and guides between the entrance edge 54 and the exit edge 56for transporting the substrate 100 is eliminated.

Because the fluid jet injectors are preferably all of equal diameter, D,and are all connected to the same plenum chamber 30, the fluid suppliedto each of the fluid jet injectors is necessarily the same, and thespeed of the fluid jets emanating from the fluid jet injectors isnecessarily also the same. If the kinematic viscosity of the suppliedfluid is denoted by nu and the speed of the fluid jets at the fluid jetinjectors is denoted by V, then the Reynolds number associated with eachof the fluid jets, defined as the ratio V*D/nu, preferably ranges fromabout 50 to about 30,000. Reynolds numbers less less than about 50 areundesirably because the corresponding fluid jets have undesirably smallmomenta. On the other hand, Reynolds numbers greater than about 30,000are undesirable because the achievement of such high Reynolds numbersrequires undesirably high plenum pressures.

In accordance with the invention, and as noted above, the row 60 offluid jet injectors is positioned closer to the entrance edge 54 (seeFIG. 3) of the surface 52 than the exit edge 56. As a result, in theoperation of the apparatus 10, the resistance to fluid flow from the row60 toward the exit edge 56, through the relatively long portion of thelayer of spent fluid covering the surface 52, is relatively high. Bycontrast, the resistance to fluid flow from the row 60 toward theentrance edge 54, through the relatively short portion of the layer ofspent fluid covering the surface 52, is relatively low. Consequently,after the fluid jets emitted by the row 60 of fluid jet injectorsimpinge upon the substrate 100, more than half the fluid associated withthe fluid jets flows counter-currently toward the entrance edge 54.Thus, undesirable dragout and re-positioning of debris is substantiallyreduced or eliminated.

Although not shown in the drawings, the injector plate 50 preferablyincludes a row of drain holes positioned adjacent the entrance edge 54,aligned transversely to the imaginary axis 110. These drain holes permitready venting of the above-described countercurrently flowing fluid.Moreover, if a pump is used to pump fluid out of the drain holes, thenthe countercurrent flow is enhanced.

Preferably, although not shown in the drawings, the injector plate 50also includes a row of drain holes positioned adjacent the exit edge 56,aligned transversely to the imaginary axis 110. These additional drainholes serve to vent the relatively small amount of fluid which flowstoward the exit edge.

As shown in FIGS. 2 and 3, the first embodiment of the inventiveapparatus 10 preferably includes a second row 70 of fluid jet injectors,penetrating the surface 52, aligned transversely to the imaginary axis110. Significantly, this second row 70 of fluid jet injectors, whichincludes fluid jet injectors 70-1, 70-2, 70-3, etc., is positionedbetween the row 60 of fluid jet injectors and the exit edge 56, and ispreferably equidistantly positioned between the entrance edge 54 and theexit edge 56. By virtue of the presence of the fluid jets emitted by thesecond row 70, the above-described countercurrent flow associated withthe fluid emitted by the first row 60 is enhanced.

To avoid imposing a torque on the substrate 100, and as depicted inFIGS. 1 and 2, the first embodiment of the inventive apparatus 10preferably includes a second plenum housing 120, containing a plenumchamber 130 into which fluid is fed under pressure via a feed tube 140.An injector plate 150 is mounted on the plenum housing 120, with rows160 and 170 of fluid jet injectors extending from the plenum chamber 130to the surface 152 of the injector plate 150. The fluid jets emitted bythe rows 160 and 170, which impinge upon the upper surface of thesubstrate 100, serve to counterbalance the fluid jets emitted by therows 60 and 70, which impinge upon the lower surface of the substrate100. As a result, undesirable torques on the substrate 100 are avoided.

With reference now to FIGS. 1, 4 and 5, a second embodiment of theinventive apparatus 10 is generally similar to the first embodiment.This second embodiment definitely includes both the plenum housing 20and the plenum housing 120, and the surfaces 52 and 152 define a channelhaving an entrance adjacent the entrance edges 54 and 154 and an exitadjacent the exit edges 56 and 156. This channel is characterized by anaxis which is oriented transversely to the entrance and exit edges54,154,56 and 156, and extends from the entrance of the channel to theexit of the channel.

In connection with the second embodiment, the substrate 100 istransported via rollers 80 and 90 through the above-defined channel in adirection which is substantially parallel to the channel axis. Thistransport occurs at a distance, H1, above the surface 52 and at adistance, H2, below the surface 152. The distances H1 and H2 need not bethe same.

As shown in FIGS. 4 and 5, the second embodiment includes at least onerow 60, and preferably two rows 60 and 70, of fluid jet injectorspenetrating the surface 52. The fluid jet injectors of the rows 60 and70 are of equal diameter, D1, and the fluid jets which they emit exitthe fluid het injectors with fluid speed V1. The fluid in these fluidjets is characterized by a kinematic viscosity nu1. Preferably, the row60 is positioned closer to the entrance edge 54 than to the exit edge56, for the reason discussed above.

The second embodiment also includes at least one row 160, and preferablytwo rows 160 and 170, of fluid jet injectors penetrating the surface152. The fluid jet injectors of the rows 160 and 170 are of equaldiameter D2, and the fluid jets which they emit exit the fluid jetinjectors with fluid speed V2. The fluid in these fluid jets ischaracterized by a kinematic viscosity nu2. The diameter D2 is notnecessarily equal to the diameter D1, the kinematic viscosity nu2 is notnecessarily equal to the kinematic viscosity nu1, and the fluid speed V2is not necessarily equal to the fluid speed V1.

In the second embodiment, like the first embodiment, the ratios H1/D1,H2/D2, V1*D1/nu1 and V2*D2/nu2 fall within the ranges given above, forthe reasons given above.

As shown more clearly in FIG. 4, the second embodiment differs from thefirst embodiment in that the row 160 is shifted relative to the row 60so that if the row 160 were to be projected onto the surface 52 (asdepicted in FIG. 4), the fluid jet injectors of the row 160 would beinterdigitated with the fluid jet injectors of the row 60. The row 170is similarly shifted relative to the row 70. The purpose of these shiftsis to ensure that fluid jets which penetrate holes in the substrate 100are unopposed by counteracting fluid jets, which substantiallyeliminated dragout in such hole.

The amount of the above-described shift, denoted Sy, is chosen so thatthe ratio Sy/S is greater than 0 but less than 1. Ratios equal to 0 and1 imply an absence of interdigitation.

It should be noted that the second embodiment has been found to beparticularly useful in rinsing substrates having holes.

With reference now to FIGS. 6,7,8 and 9, a third embodiment of theinventive apparatus is generally similar to the first and secondembodiments, and is characterized by a coordinate system x,y,z, aspictured in FIG. 6. As shown, the x-axis is parallel to the axis 110associated with the surface 52, here referred to as the transport axis.The y-axis lies in a least-squares-fit planar approximation to thesurface 52 and is perpendicular to the x-axis. The z-axis isperpendicular to both the x-axis and the y-axis.

The third embodiment differs from the second embodiment in that each ofthe fluid jet injectors in row 70 is inclined toward the entrance edge54. Moreover, each of these fluid jet injectors forms an angle, theta,with the z-axis, as measured in the counterclockwise direction in aplane defined by the z-axis and x-axis, which is greater than 0 degreesbut less than 90 degrees. Such an inclination, and range of angles,theta, enhance the countercurrent flow associated with the fluid emittedby the fluid jet injectors in the row 60, discussed above.

Preferably, the fluid jet injectors in the row 70 are also inclinedtoward the y-axis. Moreover, each such inclined fluid jet injector formsan angle, phi, with the z-axis, as measured in the clockwise directionin a plane defined by the z-axis and the y-axis, which is greater than 0degrees but less than 90 degrees. This y-axis inclination isadvantageous because it induces the fluid emitted by the fluid jetinjectors in the row 60, after impingement upon the substrate 100, toflow laterally in the direction of the y-axis, which also serves toeliminate dragout.

As shown in FIGS. 7 and 8, the third embodiment also includes a row 72of fluid jet injectors penetrating the surface 52. This third row isadvantageous because the corresponding fluid jets serve to stabilize themotions of substrates, particularly relatively thin substrates.

As also shown in FIGS. 7 and 8, the surface 54 is penetrated by rows160, 170 and 172 of fluid jet injectors, which mirror the rows 60, 70and 72 penetrating the surface 52.

It should be noted that the third embodiment has been found to beparticularly advantageous in drying substrates with holes.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

EXAMPLE 1

Rinsing of circuit boards was compared using a standard spray rinse vs.the invention apparatus. The comparison looked at conveyor length usedfor rinsing, electricity usage, flow rate of rinse water used, andresultant ionic contamination on the circuit boards.

For both parts of the experiment, one or two DSM (double spray modules),horizontally conveyorized wet processing equipment built by Chemcut inState College, Pa., were used in a counter-current rinse configuration.For the standard spray rinsing tests, two modules were used in series,with the spent waste water of the second module cascading to the firstmodule and then to waste treatment. Each module had solid cylindrical"squeegee" type rollers at its entrance and exit and had its own pumpsupplying the sprays. For the invention apparatus rinsing tests, asingle module was fitted with four pairs of the apparatus having thepreferred embodiment for rinsing as shown in FIGS. 4 and 5.

Each apparatus pair for the rinsing embodiment was characterized by twosurfaces with an an entrance-to-exit length of 1.13". Two rows, eachcontaining 327 0.030" dia. injectors, were placed in both the upper andlower surfaces at distances from the entrance edge of the device of,respectively, 0.425" and 0.692". The injectors were made by drillingholes through 0.5" thick polycarbonate plastic. Center-to-center spacingof the 0.030" dia. injector holes within each of the four rows was0.090". The injectors in the first and second rows in the upper surfacewere positioned so that their projection onto the lower surface wascentered between the injectors in the first and second rows in the lowersurface, respectively. The y-position of the injectors in the second rowin each surface was offset from the y-position of the injectors in therespective adjacent first row by 0.068". A 10 degree beveling of thefirst 0.16" of the upper and lower surfaces served as a guide for thesubstrates. Two rows of drain holes were included with diameters of0.143" and spaced center-to-center within a row 0.192" apart were placedwith centers spaced 0.220" and 0.221" from the entrance and exit edges,respectively. The distance, H1, of the lower surface from the bottom ofthe substrate was 0.10" and the distance, H2, of the upper surface ofthe device from the top of the substrate was 0.25". The rinsing fluid,water, having a viscosity, nu, of 0.01 cm**2/sec, was passed througheach of the injectors with a velocity V of 302 cm/sec, giving a Reynoldsnumber, Re, of about 2300.

Each apparatus pair had at its entrance and exit side a pair of solidcylindrical "squeegee" conveyor rollers and was provided with a pump andsump. The water was re-circulated from each respective sump to therespective apparatus, after which the water would fall back into thesump. At the same time, incoming water caused the sump water to cascadecontinuously to the stage preceding and finally to waste treatment. By"stage preceding", it is meant the stage through which the circuit boardwould travel immediately prior to the current stage. The water cascadedfrom stage to stage in the opposite direction to the direction ofcircuit board travel. This arrangement of water cascade directionrelative to product travel direction, is known as "counter-currentrinsing" in the art, is the most efficient in terms of both overallwater usage and cleanliness of the final rinse, and was used in both thespray and invention apparatus tests.

Each run consisted of ten circuit boards measuring 10×15×0.060 inchesand having a mixture of 0.050 inch and 0.018 inch diameter holes. Therewere copper traces on epoxy dielectric on the surface. The circuitboards were run at 120 inches per minute through a microetch chamber,followed by the rinse, and air dried. The microetch consisted of approx.40 g/l sodium persulfate and 40 g/l sulfuric acid dissolved in water.Resultant contamination was measured using an Omega ionograph meterwhich had been calibrated to give conductivity readings in equivalentNaCl contamination in micrograms/square inch of circuit board.

Water usage was measured with a float-type see-through flowmeter, andpower usage was determined with a hand-held current meter.

    ______________________________________                                        Results                                                                                        Ionic                                                                         contamination                                                                              Con-                                            Fluid   Water    on product   veyor  Electrical                               Delivery                                                                              usage    micro g/sq. in.                                                                            length Usage                                    Device  gal/min  (NaCl equivalent)                                                                          feet   Kilowatts                                ______________________________________                                        Spray   5        1.4          4      2.7                                      (2-stage)                                                                     Invention                                                                             1        1.7          2      1.6                                      Apparatus                                                                     (4-stage)                                                                     ______________________________________                                    

As can be seen from the data, the invention showed an essentiallyequivalent contamination level while using 40% less electricity (foursmaller pumps feeding the apparatuses of the invention used lesselectricity than the two larger pumps feeding the sprays) and generating80% less water waste by volume, all in 50% less conveyor space than thestandard spray system. As far as water usage is concerned, let it benoted that theoretically a four-stage spray rinse could use just assmall an amount of water as a four-stage rinse incorporating theinvention apparatus. However, such a four-stage spray rinse would occupyfour times as much conveyor space and would consume three and one-thirdtimes as much electricity as the invention apparatus.

EXAMPLE 2

Drying of circuit boards was compared using the invention apparatusversus two state-of-the art dryers. Comparison results were measured forboth high and normal aspect-ratio thru-holes in terms of electricityusage and conveyor length.

The state-of-the art dryer used as a basis of comparison for hi-aspectratio thru-holes was a SHD ("small hole dryer") built by InternationalSupplies of Parma, Italy. Circuit boards run through this machine wereapproximately 0.300 inches thick and 24×28 inches in width and lengthwith thousands of approx. 0.015 inch dia. thru-holes. The dryer usedfour "push-pull" slotted manifolds run by a turbine blower that forcedpressurized air against one side of the circuit board and suction to theopposing side. The push-pull was alternated so that the pressure sidealternated up, down, up and then down. Following the forced-air slottedblowers were two heated fan blowers that recirculated hot air. When thecircuit boards were conveyed through this configuration at 1meter/minute, many of the thru-holes were still wet, leading to unwantedstains that were deleterious in subsequent processes. A single pair ofthe invention apparatuses with the preferred drying embodiment as shownin FIGS. 6-9 were installed with a turbine blower feeding each side.

The apparatus pair for the drying embodiment was characterized by twosurfaces with an entrance-to-exit length of 2.25". Three rows, eachcontaining 171 0.043" dia. injectors, were placed in both the upper andlower surfaces at distances from the entrance edge of the device of,respectively, 0.500", 0.650", and 1.125". The injectors in the upper andlower surfaces, respectively, were made by drilling holes through 0.3"and 0.5" thick aluminum metal. Center-to-center spacing of the 0.043"dia. injector holes within each of the four rows was 0.150". Theinjectors in the first, second and third rows in the upper surface werepositioned so that their vertical projection onto the lower surface wascentered between the injectors in the first, second, and third rows inthe lower surface, respectively. The y-position of the injectors in thesecond and third rows in each surface was offset from the y-position ofthe injectors in the adjacent first row by 0.050" and 0.100",respectively. An 18 degree beveling of the first 0.375" of the upper andlower surfaces served as a guide for the substrates. The injectors inthe upper and lower surfaces were drilled at a 15 degree angle so thatjets issuing from them were tilted towards the entrance of the device.The distance, H1, of the lower surface from the bottom of the substratewas 0.050" and the distance, H2, of the upper surface of the device fromthe top of the substrate was 0.250". The drying fluid was air having aviscosity, nu, of 0.17 cm**2/sec, and was passed through each of theinjectors with a velocity V of 9000 cm/sec, giving a Reynolds number,Re, of about 5800.

With the invention installed, at 1 meter/min conveyor speed, and withthe two heated blowers off, all of the thru-holes were dry.

The state-of-the-art dryer used as a basis of comparison for normalaspect-ratio thru-holes was a "TMDM" dryer built by Chemcut of StateCollege, Pennsylvania. Circuit boards run through this machine wereapproximately 0.060 inch thick and 10×15 inches in width and length. Thedryer used several different blowers and manifolds and also used aheated rinse with the intent to allow the water retained on the panel todry more rapidly. When panels were sent through this machine at 2meters/minute they dried sufficiently, but when they were sent throughat 3 meters/minute they still had wet spots. In comparison, the samedrying apparatus pair used in the hi-aspect ratio tests above dried thepanels completely at 3 meters/minute conveyor speed.

To qualitatively test the amount of air venting from the entrance of thedevice vs. from the exit, a strip of paper was held verticallyimmediately before and behind the apparatus. Using this method, it wasnoted that a strong positive flow of air issued from the deviceentrance, but that a neutral if not slightly negative flow of air wasissuing from the device exit. In other words, it appeared that air wasactually being sucked into the exit side of the device, probably due toBernoulli effects. From these observations, it is clear that theinvention produces an exceptionally good counter-current flow of airagainst the travelling substrate, which is also advantageous toefficient drying.

A summary of the drying comparison follows:

    ______________________________________                                                      Conveyor                                                                              Electrical                                                            length  Usage                                                                 feet    Kilowatt                                                ______________________________________                                        Low aspect-ratio                                                              State-of-the art                                                                              4         10                                                  Invention Apparatus                                                                           .5        4                                                   High aspect-ratio                                                             State-of-the art                                                                              5.5       >15                                                 Invention Apparatus                                                                           .5        4                                                   ______________________________________                                    

As can be seen, all other things being equal, the invention is veryeconomical in terms of both conveyor space and electrical usage. Thefact that heated air is not needed is also a plus since this reduces therisk of oxidation of the copper traces on the circuit boards.

We claim:
 1. Fluid treatment apparatus, comprising:at least a firstsurface, of finite dimensions, including an entrance edge and an exitedge and characterized by an axis extending from said entrance edge tosaid exit edge; means for transporting a substrate over said surface ata distance, H, from said surface, from said entrance edge to said exitedge along a direction which is substantially parallel to said axis,Characterized In That said apparatus further comprises at least a firstrow of at least two, spaced-apart fluid jet injectors, said first rowbeing aligned transversely to said axis, said at least two fluid jetinjectors penetrating said surface and serving to produce a first row ofat least two fluid jets which impinge upon said substrate, each of saidfluid jet injectors being characterized by a diameter, D, with the ratioH/D ranging from about 0.2 to about 15, and said first row of fluid jetinjectors being positioned closer to said entrance edge than to saidexit edge, whereby after said first row of fluid jets is impinged uponsaid substrate, more than half the fluid associated with said first rowof fluid jets flows in a direction substantially opposite to thedirection of transport of said substrate.
 2. The fluid treatmentapparatus of claim 1, wherein each of said fluid jets is characterizedby a fluid speed, V, at said fluid jet injectors, and the fluid of saidfluid jets is characterized by a kinematic viscosity, nu, and wherein aReynolds number associated with each of said fluid jets, defined as theratio V*D/nu, ranges from about 50 to about 30,000.
 3. The fluidtreatment apparatus of claim 1, further comprising at least a second rowof at least two, spaced-apart fluid jet injectors, said second row beingaligned transversely to said axis, the fluid jet injectors of saidsecond row also penetrating said surface and also serving to produce asecond row of at least two fluid jets which impinge upon said substrate,said second row being positioned between said first row and said exitedge.
 4. The fluid treatment apparatus of claim 3, wherein said secondrow of fluid jet injectors is positioned equidistantly between saidentrance edge and said exit edge.
 5. The fluid treatment apparatus ofclaim 1, further comprising at least a first row of at least two,spaced-apart drain holes which penetrate said surface, said first row ofdrain holes being aligned transversely to said axis and being positionedbetween said entrance edge and said first row of fluid jet injectors. 6.The fluid treatment apparatus of claim 5, further comprising means forpumping fluid out of said first row of drain holes.
 7. The fluidtreatment apparatus of claim 5, further comprising at least a second rowof at least two, spaced-apart drain holes, said second row of drainholes being aligned transversely to said axis and being positionedbetween said first row of fluid jet injectors and said exit edge. 8.Fluid treatment apparatus, comprising: first and second spaced-apartsurfaces, each having finite dimensions, defining a channel therebetweenhaving an entrance, an exit and an axis extending from said entrance tosaid exit;means for transporting a substrate through said channel,between said first and second surfaces, in a direction substantiallyparallel to said axis, from said entrance to said exit, Characterized InThat said apparatus further comprises at least a first row of at leasttwo, spaced-apart fluid jet injectors, said first row being alignedtransversely to said axis, the fluid jet injectors of said first rowpenetrating said first surface and serving to produce a first row of atleast two, spaced-apart fluid jets which impinge upon a lower surface ofsaid substrate. at least a second row of at least two, spaced-apartfluid jet injectors, said second row being aligned transversely to saidaxis, the fluid jet injectors of said second row penetrating said secondsurface and serving to produce a second row of at least two,spaced-apart fluid jets which impinge upon an upper surface of saidsubstrate, said second row of fluid jet injectors being positionedrelative to said first row of fluid jet injectors so that if said secondrow of fluid jet injectors were to be projected onto said first surface,the fluid jet injectors of said second row would be substantiallyinterdigitated with the fluid jet injectors of said first row.
 9. Thefluid treatment apparatus of claim 8, wherein each of the fluid jetinjectors of said first row is characterized by a first diameter, D1,and each of the fluid jet injectors of said second row is characterizedby a second diameter, D2, and wherein said means serves to transportsaid substrate through said channel at a first distance, H1, from saidfirst surface and at a second distance, H2, from said second surface,and wherein the ratio H1/D1 ranges from about 0.2 to about 15 and theratio H2/D2 ranges from about 0.2 to about
 15. 10. The fluid treatmentapparatus of claim 9, wherein each of the fluid jets of said first rowof fluid jets is characterized by a fluid speed, V1, at the first row offluid jet injectors, the fluid associated with each of the fluid jets ofsaid first row of fluid jets is characterized by a kinematic viscosity,nu1, and each of the fluid jets of said first row of fluid jets ischaracterized by a Reynolds number, defined as the ratio V1*D1/nu1,which ranges from about 50 to about 30,000.
 11. The fluid treatmentapparatus of claim 10, wherein each of the fluid jets of said second rowof fluid jets is characterized by a fluid speed, V2, at the second rowof fluid jet injectors, the fluid associated with each of the fluid jetsof said second row of fluid jets is characterized by a kinematicviscosity, nu2, and each of the fluid jets of said second row of fluidjets is characterized by a Reynolds number, defined as the ratioV2*D2/nu2, which ranges from about 50 to about 30,000.
 12. The fluidtreatment apparatus of claim 8, wherein each of said first and secondrows of fluid jet injectors is positioned closer to said entrance thanto said exit.
 13. The fluid treatment apparatus of claim 12, furthercomprising a third row of at least two, spaced-apart fluid jetinjectors, said third row being aligned transversely to said axis, thefluid jet injectors of said third row penetrating said first surface andserving to produce a third row of at least two fluids jets which impingeupon a lower surface of said substrate, said third row of fluid jetinjectors being positioned between said first row of fluid jet injectorsand said exit.
 14. The fluid treatment apparatus of claim 13, furthercomprising a fourth row of at least two, spaced-apart fluid jetinjectors, said fourth row being aligned transversely to said axis, thefluid jet injectors of said fourth row penetrating said second surfaceand serving to produce a fourth row of at least two fluid jets whichimpinge upon an upper surface of said substrate, said fourth row beingpositioned between said second row of fluid jet injectors and said exit,and said fourth row being positioned relative to said third row so thatif the fluid jet injectors of said fourth row were to be projected ontosaid first surface, the fluid jet injectors of said fourth row would besubstantially interdigitated with the fluid jet injectors of said thirdrow.
 15. Fluid treatment apparatus, comprising:at least a first surface,of finite dimensions, including an entrance edge and an exit edge, saidfirst surface being characterized by a transport axis extending fromsaid entrance edge to said exit edge and a coordinate system includingan x-axis which is parallel to said transport axis, a y-axis which liesin a least-squares-fit planar approximation to said first surface and isperpendicular to said x-axis, and a z-axis which is perpendicular toboth said x-axis and said y-axis; means for transporting a substrateover said surface at a distance from said surface, from said entranceedge to said exit edge along a direction which is substantially parallelto said transport axis, Characterized In That said apparatus furthercomprises at least a first row of at least two, spaced-apart fluid jetinjectors and a second row of at least two, spaced-apart fluid jetinjectors, said first row being aligned transversely to said transportaxis and the fluid jet injectors of said first row penetrating saidfirst surface and serving to produce a first row of at least two fluidjets which impinge upon said substrate, said second row being alignedtransversely to said axis and the fluid jet injectors of said second rowpenetrating said first surface and serving to produce a second row of atleast two fluid jets which impinge upon said substrate, said second rowof fluid jet injectors being positioned at a greater x-coordinatelocation than said first row of fluid jet injectors, and at least eachof the fluid jet injectors of said second row of fluid jet injectorsbeing inclined toward said entrance edge with each forming an angle withsaid z-axis, as measured in the counterclockwise direction in a planedefined by said z-axis and said x-axis, which angle is greater than 0degrees but less than 90 degrees, whereby after said first row of fluidjets is impinged upon said substrate, more than half the fluidassociated with said first row of fluid jets flows in a directionsubstantially opposite to the direction of transport of said substrate.16. The fluid treatment apparatus of claim 15, wherein each of the fluidjet injectors of said second row of fluid jet injectors is also inclinedtoward said y-axis, each of the inclined fluid jet injectors forming anangle with said z-axis, as measured in the clockwise direction in aplane defined by said z-axis and said y-axis, which is greater than 0degrees but less than 90 degrees.
 17. The fluid treatment apparatus ofclaim 15, wherein said first row of fluid jet injectors is closer tosaid entrance edge than to said exit edge.
 18. A method for treating asubstrate with a fluid, comprising the steps of:transporting saidsubstrate over a surface, of finite dimensions, including an entranceedge and an exit edge and characterized by an axis extending from saidentrance edge to said exit edge, said transporting being carried out ata distance, H, from said surface, from said entrance edge to said exitedge, along a direction which is substantially parallel to said axis;and impinging at least a first row of at least two fluid jets upon saidsubstrate, emanating from a first row of at least two, spaced-apartfluid jet injectors, said first row of fluid jet injectors being alignedtransversely to said axis and penetrating said surface, and thereforesaid first row of fluid jets is aligned transversely to said axis, eachof said fluid jet injectors being characterized by a diameter, D, theratio H/D ranging from about 0.2 to about 15, said first row of fluidjet injectors being positioned closer to said entrance edge than to saidexit edge, whereby after said impinging step, more than half the fluidassociated with said first row of fluid jets flows in a directionsubstantially opposite to the direction of transport of said substrate.19. The method of claim 18, wherein each fluid jet of said first row offluid jets is characterized by a fluid speed, V, at said first row offluid jet injectors, and the fluid of said fluid jets is characterizedby a kinematic viscosity, nu, and wherein during said impinging step, aReynolds number associated with each of said fluid jets, defined as theratio V*D/nu, ranges from about 50 to about 30,000.
 20. The method ofclaim 18, further comprising the step of impinging at least a second rowof at least two fluid jets upon said substrate, emanating from a secondrow of at least two, spaced-apart fluid jet injectors, said second rowof fluid jet injectors being aligned transversely to said axis andpenetrating said surface, and therefore said second row of fluid jets isaligned transversely to said axis, said second row of fluid jetinjectors being positioned between said first row of fluid jet injectorsand said exit edge and the areas of impingement of said second row offluid jets upon said substrate being between the areas of impingement ofsaid first row of fluid jets upon said substrate and said exit edge. 21.A method of treating a substrate with a fluid, comprising the stepsof:transporting a substrate between first and second spaced-apartsurfaces, of finite dimensions, defining a channel therebetween havingan entrance, an exit and an axis extending from said entrance to saidexit, said transporting step occurring along a direction substantiallyparallel to said axis, from said entrance to said exit; and impinging atleast a first row of at least two fluid jets upon a lower surface ofsaid substrate, said first row of fluid jets emanating from a first rowof at least two fluid jet injectors which penetrate said first surface,and impinging at least a second row of at least two fluid jets upon anupper surface of said substrate, said second row of fluid jets emanatingfrom a second row of at least two fluid jet injectors which penetratesaid second surface, said second row of fluid jets being positionedrelative to said first row of fluid jets so that if said second row offluid jets were to be projected onto said first surface, said second rowof fluid jets would be substantially interdigitated with said first rowof fluid jets.
 22. The method of claim 21, wherein each of said firstrow of fluid jet injectors is characterized by a first diameter, D1, andeach of said second row of fluid jet injectors is characterized by asecond diameter, D2, and wherein said step of transporting saidsubstrate through said channel occurs at a first distance, H1, from saidsurface and at a second distance, H2, from said second surface, andwherein the ratio H1/D1 ranges from about 0.2 to about 15 and the ratioH2/D2 ranges from about 0.2 to about
 15. 23. The method of claim 22,wherein each of said first row of fluid jets is characterized by a fluidspeed, V1, at said first row of fluid jet injectors, the fluidassociated with each of said first row of fluid jets is characterized bya kinematic viscosity, nu1, and wherein during said impinging step, eachof said first row of fluid jets is characterized by a Reynolds number,defined as the ratio V1*D1/nu1, which ranges from about 50 to about30,000.
 24. The method of claim 23, wherein each of said second row offluid jets is characterized by a fluid speed, V2, at said second row offluid jet injectors, the fluid associated with said second row of fluidjets is characterized by a kinematic viscosity, nu2, and wherein duringsaid impinging step, each of said second row of fluid jets ischaracterized by a Reynolds number, defined as the ratio V2*D2/nu2,which ranges from about 50 to about 30,000.
 25. A method of treating asubstrate with a fluid, comprising the steps of:transporting saidsubstrate over a surface, of finite dimensions, including an entranceedge and an exit edge and characterized by a transport axis extendingfrom said entrance edge to said exit edge and a coordinate systemincluding an x-axis which is parallel to said transport axis, a y-axiswhich lies in a least-squares-fit planar approximation to said surfaceand is perpendicular to said x-axis, and a z-axis which is perpendicularto both said x-axis and said y-axis, said transporting step beingcarried out at a distance from said surface, from said entrance edge tosaid exit edge, along a direction which is substantially parallel tosaid transport axis; and impinging at least a first row of at least twofluid jets, and a second row of at least two fluid jets, upon saidsubstrate, said first row of fluid jets emanating from a first row of atleast two, spaced-apart fluid jet injectors which penetrate said surfaceand said second row of fluid jets emanating from a second row of atleast two, spaced-apart fluid jet injectors which penetrate saidsurface, at least each of said second row of fluid jets being inclinedtoward said entrance edge and forming an angle with said z-axis, asmeasured in the counterclockwise direction in a plane defined by saidz-axis and said x-axis, which is greater than 0 degrees but less than 90degrees, whereby after said impinging step, more than half the fluidassociated with said first row of fluid jets flows in a directionsubstantially opposite to the direction of transport of said substrate.26. The method of claim 25, wherein each of said second row of fluidjets is inclined toward said y-axis, with each such fluid jet forming anangle with said z-axis, as measured in the clockwise direction in aplane defined by said z-axis and said y-axis, which is greater than 0degrees but less than 90 degrees.
 27. The method of claim 25, whereineach of said first row of fluid jets impinges upon said substrate at anx-location which is closer to said entrance edge than to said exit edge.